Influence of Potamogeton crispus growth on nutrients in the sediment and water of Lake Tangxunhu

An incubation experiment was performed on Potamogeton crispus (P. crispus) using sediment collected from Lake Tangxunhu in the center of China, in order to determine the effects of plant growth on Fe, Si, Cu, Zn, Mn, Mg, P, and Ca concentrations in the sediments and overlying waters. After 3 months of incubation, Ca, Mg, and Si concentrations in the water column were significantly lower, and P and Cu concentrations were significantly higher than in unplanted controls. The effect of P. crispus growth on sediment pore waters and water-extractable elements varied. Concentrations of Ca, Mg, Si, Fe, Cu, and Zn were significantly higher, and P was significantly lower, than in pore waters of the control. Water-extracted concentrations of Fe, Mg, and Si in the sediments were lower, and P was higher, than in the control. Presence of P. crispus generally enhanced concentration gradients of elements between pore waters and overlying waters but not for P. The growth of P. crispus was associated with an increase in water pH and formation of root plaques, resulting in complex effects on the sediment nutritional status

Wetland ecological risk assessment and management: Taking Wenzhou Sanyang Wetland as a case study

Based on the traditional framework of wetland ecological risk assessment, this thesis proposed a new method by considering two major pollution types faced by wetlands, including heavy metal pollution and water eutrophication. Artificial neural network (ANN) method was applied to evaluate the eutrophication risk level, while an improved potential ecological risk index was used to estimate the risk of heavy metals in surface sediments. Then, Fuzzy set theory was used to combine the two risk levels to obtain a general risk level, which could be used for recommending appropriate risk management actions. The Sanyang Wetland in Wenzhou, China was used as a case study to demonstrate the proposed wetland ecological risk assessment method. This thesis indicated that the new framework of wetland ecological assessment could provide a risk level of objectives and give corresponding suggestions to decision making.wetland ecological risk assessmentpollution types faced by wetlandsheavy metal pollution water eutrophicationsurface sedimentswater eutrophicatio

A Historical Sedimentary Record of Mercury in a Shallow Eutrophic Lake: Impacts of Human Activities and Climate Change

Mercury and its derivatives are hazardous environmental pollutants and could affect the aquatic ecosystems and human health by biomagnification. Lake sediments can provide important historical information regarding changes in pollution levels and thus trace anthropogenic or natural influences. This research investigates the 100-year history of mercury (Hg) deposition in sediments from Chao Lake, a shallow eutrophic lake in China. The results indicate that the Hg deposition history can be separated into three stages (pre-1960s, 1960s–1980s, and post-1980s) over the last 100 years. Before the 1960s, Hg concentrations in the sediment cores varied little and had no spatial difference. Since the 1960s, the concentration of Hg began to increase gradually, and showed a higher concentration of contamination in the western half of the lake region than in the eastern half of the lake region due to all kinds of centralized human-input sources. The influences of anthropogenic factors and hydrological change are revealed by analyzing correlations between Hg and heavy metals (Fe, Co, Cr, Cu, Mn, Pb, and Zn), stable carbon and nitrogen isotopes (δ13C and δ15N), nutrients, particle sizes, and meteorological factors. The results show that Hg pollution intensified after the 1960s, mainly due to hydrological change, rapid regional development and urbanization, and the proliferation of anthropogenic Hg sources. Furthermore, the temperature, wind speed, and evaporation are found to interactively influence the environmental behaviors and environmental fate of Hg

Spatial distributions, fractionation characteristics, and ecological risk assessment of trace elements in sediments of Chaohu Lake, a large eutrophic freshwater lake in eastern China

The concentrations, spatial distribution, fractionation characteristics, and potential ecological risks of trace elements (Cu, Pb, Zn, Cr, Ni, and Co) in the surface sediment samples collected from 32 sites in Chaohu Lake were investigated. The improved BCR sequential extraction procedure was applied to analyze the chemical forms of trace elements in sediments. The enrichment factor (EF), sediment quality guidelines (SQGs), potential ecological risk index (PERI), and risk assessment code (RAC) were employed to evaluate the pollution levels and the potential ecological risks. The results found that the concentrations of Cu, Pb, Zn, Cr, Ni, and Co in the surface sediments were 78.59, 36.91, 161.84, 98.87, 38.92, and 10.09 mg kg(-1), respectively. The lower concentrations of Cu, Pb, Zn, Cr, and Ni were almost found in the middle part of the lake, while Co increased from the western toward the eastern parts of the lake. Cr, Ni, Co, and Zn predominantly existed in the residual fractions, with the average values of 76.35, 59.22, 45.60, and 44.30%, respectively. Cu and Pb were mainly combined with Fe/Mn oxides in reducible fraction, with the average values of 66.4 and 69.1%, respectively. The pollution levels were different among the selected elements. Cu had the highest potential ecological risk, while Cr had the lowest potential ecological risk

Spatial and temporal variability of trace metal concentrations and speciation in Connecticut surface waters

In this research, two studies were conducted to investigate the spatial distribution and seasonal variation of trace metal concentrations and speciation in Connecticut surface waters. In the first part, along with the monthly vertical profile of background biogeochemistry parameters (pH, Temperature, Dissolved oxygen, Major ions, Total dissolved solids, Nutrients, Acid neutralizing capacity, dissolved organic carbon), competitive ligand exchange – adsorptive cathodic stripping voltammetry was used to determine cobalt speciation in Linsley Pond, North Branford. Vitamin B12 (VB12) via enzyme-linked immunosorbent assay (ELISA) was measured in an American stratified lake for the very first time. During summer stratification, the patterns of Co and Mn are similar, very low in surface water, and reach the highest concentration across the redoxcline caused by the bacterial activity of PSB. The different patterns of Co in the hypolimnion between 2017 and 2018 are caused by the formation of CoS. Higher epilimnetic particulate Co is observed in July and August, corresponding to the highest DO and DOC, respectively, indicating that cobalt is closely related to the photosynthesis of phytoplankton, the metabolism of organisms. Total dissolved Co was dominated by its natural organic ligand complex. The measured VB12 ranged from 0.033 – 0.048 nM, comparable to [Co2+] detected in freshwater systems. In the second part, an estuary with self-regulating tide gates (SRTGs) installed was studied about the combination of watershed flood flow and tidal flushing impact at both short and long time scales. The cycling of particle-reactive contaminants represented by the metals was studied over the course of several tidal cycles during both baseflow and storm event conditions. TSS and turbidity were highly correlated at the inlet but not consistently at the tide gates. In contrast, at the tide gates, TSS was dominantly affected by tides unless extreme storms. Cobalt and 7Be budgets over one tidal cycle were determined. Cobalt was mostly in the dissolved form at the tide gates and the inlet, under baseflow conditions. However, particulate Co became the dominant component of total Co at the inlet during storm events, contributed by sediments delivered from the watershed. According to the 7Be mass balance over a tidal cycle, perhaps owing to the large ratio of its watershed to estuary, most of the 7Be (86%) enters the West River estuary from its watershed. Direct atmospheric deposition is a significant but lesser source. In addition to 3% decay in the water column, only 1.5% of 7Be is gained from Long Island Sound via tidal flushing. More than 40% of added 7Be is deposited in sediments within the estuary during a single tidal cycle, meanwhile, Co received from the watershed (ca. 60 g) is approximately equal to the net loss of Co by the tidal exchange. The West River estuary is a tight trap for contaminants that behave like Be, but not for Co or probably other substances that are not strongly particle reactive as well

Bioavailability and Migration Features of Metals in “Bottom Sediments – Water” System under the Action of Different Environmental Factors

This review considers and summarizes findings of the studies on metals’ coexisting forms in bottom sediments of surface water bodies. This makes it possible to assess metals’ migration ability in the “bottom sediments – water” system and their potential bioavailability for hydrobionts. The coexisting forms of metals in bottom sediments depend on their chemical properties and the component composition of the solid phase. Metals are distributed among exchangeable, carbonate, oxide, organic and residual fractions of bottom sediments. The highest migration ability is observed for metals contained in the first three fractions. Metals migration from organic and residual fractions hardly ever takes place. The oxygen regime, pH and redox potential, total dissolved solids and water temperature, concentration and component composition of organic substances affect the exchange of metals between bottom sediments and overlying water. The metal mobility in the “bottom sediments – water” system will increase under conditions of climate change. This is because cases of dissolved oxygen deficiency become more common, the total dissolved solids get higher in concentration, and pH and redox potential is reduced. Therefore, the development of methods to reduce metals migration from bottom sediments is a relevant task, which is discussed in the present paper.

Geochemistry of water and sediment

Access to drinking water is one of the largest problems of modern times, and water pollution is a growing problem worldwide. Increased concentrations of different toxic substances, especially heavy metals, affect biodiversity and are hazardous for human health. Sediment may act as a sink for a huge number of toxic substances and should, therefore, be investigated in addition to water, as it contains a record of previous pollution. Geochemical investigations of aquatic sediments in freshwater and marine environments present excellent insights into the state of pollution of investigated water bodies and their ecosystems. The chemical composition of sediment is informative, both in investigations of mineral resources of a particular region for mining purposes and in tracing contamination from different sources. Pollution affects all sources of drinking water—ground, spring, river, and lake. The interaction of water and sediment is of special importance, as sediment can also release heavy metals and act as a source of pollution. Systematic geochemical investigations of river sediments and their quality in the broader region of SE Europe started in 1989 in Croatia [1], with pioneering study of heavy metals in sediments of the Krka River Estuary, Croatia. This study was the first attempt to determine anthropogenic influence in sediments. First systematic assessment of multi-elemental composition of stream sediments for evaluating sediment quality guidelines in a large drainage basin of this region was performed in 2005 and 2007 on example of Kupa River drainage basin (Croatia, Slovenia, Bosnia and Herzegovina) [2, 3]. During the following years, Croatian scientists expanded their research with introducing the new fast and efficient method of magnetic susceptibility applied on sediment con-tamination with heavy metals research in Croatia and nearby countries [4]. Their research and collaboration expanded through the region and among other we highlight the fruitful collaboration with team from Centre of Excellence of University of Belgrade, Serbia. Research expertise of Croatian and Serbian partners is complementary and currently joint research on example locations in Croatia (Kupa River) and Serbia (Vlasina River) are under way. Until now it resulted in published paper on thematic of geochemical fractionation and risk assessment of potentially toxic elements in sediments from Kupa River, Croatia [5]. Croatian partners are disseminating to Serbian partners their experience and knowledge about river sediment research and monitoring, as well as about introducing of magnetic methods, while Serbian partners are disseminating to Croatian partners their experience in geochemical fractionation and risk assessment of potentially toxic elements in sediments. Intensive collaboration between Croatian and Serbian scientists resulted in joint idea to launch a Special Issue of Water focusing on geochemistry of water and sediment. This idea was accepted from Editorial Board of Water and Dr. Stanislav Frančišković-Bilinski from Ruđer Bošković Institute, Zagreb, Croatia and Dr. Sanja Sakan from Centre of ex-cellence of the University of Belgrade, Serbia, have been confirmed as Editors of the Special Issue under the title “Geochemistry of Water and Sediment”, within the section “Aquatic Systems—Quality and Contamination”. The purpose of this Special Issue was to publish original, high-quality research papers, as well as review articles, addressing recent advances in water and aquatic sediment research, new methods and developments in monitoring, as well as legislative development. This Special Issue was announced in May 2019 and opened for submissions with a deadline of 30 December 2020. However, due to the pandemic and lockdown over most of the world in spring 2020, the deadline was extended until 30 November 2020, when submissions for this Special Issue were closed. A total of 12 papers were submitted for publication and they have undergone a scrutinized review process. Eventually, ten papers passed the rigorous review by at least two recognized international reviewers and extensive editorial checks. The papers compiled in this Special Issue show a wide variety of topics

A review of the effect of trace metals on freshwater cyanobacterial growth and toxin production

© 2019 Author(s). Cyanobacterial blooms are becoming more common in freshwater systems, causing ecological degradation and human health risks through exposure to cyanotoxins. The role of phosphorus and nitrogen in cyanobacterial bloom formation is well documented and these are regularly the focus of management plans. There is also strong evidence that trace metals are required for a wide range of cellular processes, however their importance as a limiting factor of cyanobacterial growth in ecological systems is unclear. Furthermore, some studies have suggested a direct link between cyanotoxin production and some trace metals. This review synthesises current knowledge on the following: (1) the biochemical role of trace metals (particularly iron, cobalt, copper, manganese, molybdenum and zinc), (2) the growth limitation of cyanobacteria by trace metals, (3) the trace metal regulation of the phytoplankton community structure and (4) the role of trace metals in cyanotoxin production. Iron dominated the literature and regularly influenced bloom formation, with 15 of 18 studies indicating limitation or colimitation of cyanobacterial growth. A range of other trace metals were found to have a demonstrated capacity to limit cyanobacterial growth, and these metals require further study. The effect of trace metals on cyanotoxin production is equivocal and highly variable. Better understanding the role of trace metals in cyanobacterial growth and bloom formation is an essential component of freshwater management and a direction for future research